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The phyletic implications of spermathecal structure in the Raninidae (Decapoda: Brachyura)
Author(s) -
HARTNOLL R. G.
Publication year - 1979
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1979.tb07714.x
Subject(s) - spermatheca , biology , anatomy , phyletic gradualism , sternum , decapoda , zoology , crustacean , botany , phylogenetics , biochemistry , sperm , gene
The true crabs or Brachyura can be divided into a primitive section with integumental spermathecae unconnected with the oviducts, and an advanced section with spermathecae formed as dilations of the oviducts: no intermediate forms are known. Previously the Raninidae, one of the primitive families, has been considered to have a single median sper‐matheca, as in the presumed ancestral Astacura. This conflicted with their generally more evolved condition compared to the other primitive families. This investigation shows that the basic raninid structure is as in other primitive crabs, with paired spermathecae lying within endosternite 7/8. Due to the acute dorsal flexion of the posterior sternites the spermathecae have come to open anteriorly on sternite 7 rather than on sternal suture 7/8, and due to narrowing of the sternum the paired openings may appear as a single median one. This revised structure confirms the Raninidae as the most advanced of the primitive Brachyura, but unfortunately does not contribute to an understanding of the course of evolution of the spermathecal condition in the advanced Brachyura.